The miniDVI is limited to 24" resolutions - though with a dual head 2 go you should be able to split that and run two 17" monitors.

You can get a USB to DVI adapter to add 3rd monitor (and more) - though this monitor will be slower than the others. Good for palettes and email and such though. And the USB adapters don't support 24" monitors (max out around 1600x1200, not 1920x1200).